Critics accuse the government of failing to properly equip soldiers and refusing requests for more troops.
Shadow defence secretary Dr Liam Fox has told the BBC the Conservatives would be "extremely likely" to agree to short-term requests for extra manpower if they were in office.
Gen Dannatt told the BBC it was "critical" to tackle the problem of improvised bombs.
Doing this required more coalition or Afghan personnel to build intelligence, better "overhead surveillance" of Taliban activity and greater technical ability to see where they were planting explosives, he said.
"That will be a shopping list that I'll bring back," he said.
Continued heavy casualties would cause the British public to doubt the value of the mission, which would be a strategic disaster, he said.
Gen Dannatt repeated calls for the Ministry of Defence to focus its priorities towards the "land environment", away from navy and air force needs, when carving up its £34bn budget.
He has previously called for more British, American or Afghan "boots on the ground" but he said military chiefs had never made a direct request for 2,000 extra personnel.
On Thursday, the prime minister refused to directly confirm or deny whether this request had been received, when he appeared before the Commons liaison committee.
However, the general said Nato commanders may shortly present a case for a "short-term uplift" in numbers.
"Our government will have to confront it, if asked, for about 12 to 18 months until the Afghan army can get the right strength down here [in Helmand]," he said.
It has been suggested that force levels could be reduced to 8,300 after elections planned for next month but that would be wrong, he added.
Earlier this week, the general revealed he was being flown around Helmand in an American helicopter because no British alternative was available.
Ministers say all coalition helicopters in Afghanistan are available for use by all Nato allies.
The general's comments come during a month in which 16 British soldiers have died - 12 killed by roadside bombs.
Mr Fox told BBC Radio 4's Today programme it was "extremely likely" the Conservatives - if in power - would agree to a request for more British troops in the short term.
"If we had a direct request from the head of the armed forces that they needed something specific to maximise the chance of success of the mission and minimise the risk to our forces, of course we would have to say 'yes' to that," he said.
Mr Fox said he understood the request for extra troops had been to allow for the training of Afghan forces.
Providing more personnel for this would be "easier" than if they were needed for frontline duties, which would require additional equipment, he said.
Lord Mandelson told the BBC the last thing troops needed was for opposition parties to seek "political advantage" on issues relating to Afghanistan, rather than giving united backing.
The increase in UK casualties has come as coalition troops conduct an offensive designed to increase security ahead of the Afghan elections.
Col Richard Kemp, who commanded troops in Afghanistan in 2003, said extra equipment can help but that casualties are unavoidable.
"People who think that by a couple more helicopters, slightly different armoured vehicles, we're going to eliminate all casualties, we're not."
So far, 185 UK service personnel have now died in Afghanistan since 2001 - more than the 179 who were killed during the war in Iraq.
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